The use of modular link conveyors in industry enjoys increasing popularity. Particularly for conveying food articles or consumer products, especially in packages or in semi-packaged form, the modular link conveyor represents the overwhelming choice of those in the industry looking for a long-lasting, low cost conveying solution. In the recent past, significant advances in the development of such have been made so as to provide more efficient handling of an even larger variety of food articles, packages and containers, as well as other types of articles and products.
One of the most popular types of modular link conveyor systems on the market today, if not the most popular, is manufactured and sold by the assignee of the present invention under THE DESIGNER SYSTEM and WHISPERTRAX trademarks, and illustrated and claimed in prior U.S. Pat. No. 4,953,693, Sep. 4, 1990 and U.S. Pat. No. 5,031,757, issued Jul. 16, 1991 (both of which patents are fully incorporated herein by reference). Since the time of these early patents in the art, the significant advances have been fast in coming to provide an even more efficient operation and better handling and transporting of articles and products.
Despite eliminating the deleterious catenary approach prevalent in the prior art and providing the advantageous secure holding by the guide links, an aesthetic problem sometimes arises from use of the preferred stainless steel connector to connect the modular links forming the conveyor belt. Specifically, wear particles, or “black oxide” from the connector may become embedded in light-colored links made from certain polymer materials, including Acetal (which, despite being an abrasion-resistant material, is considered to be fairly abrasive itself). Although not a problem from a durability or reliability standpoint, the resultant appearance of the dark-colored wear particles embedded in the links can lead to unfounded concerns regarding cleanability of the belt, especially in applications where food products are being conveyed. Particles separated from the stainless steel rod also further compound the problem by becoming embedded in the adjacent surface of the link, which then accelerate the wear.
In the past, others have proposed various types of modular link connectors, or “hinge pins” as they are sometimes called, made of polymer materials. While such polymer connectors do not create the same “black oxide” as stainless steel, they are not as able to resist significant shear loading and are also substantially more susceptible to creep. Over time, this creep causes polymer rods to assume an irregular, or “wavy,” profile. This profile not only compromises the appearance and operation of the belt, but also makes it more difficult to remove the rods for replacement. Additionally, the dimensional pitch of the chain is lost, resulting in premature sprocket wear.
More recently, U.S. Pat. No. 6,648,129 to Sedlacek describes a “two material” hinge pin arrangement in which a rod made of a rigid material (such as steel) slidably receives a urethane outer tube. According to the patent, the urethane tube forms a high friction material that preferably rotates relative to the underlying rod to facilitate articulation (ostensibly as the result of particles becoming embedded in the space between the tube and the rod). Besides creating an arrangement that can be impossible to clean in an easy and economical fashion, the high friction surface of the outer tube may actually cause significant wear on the links, as well as the underlying rod in the event of relative rotation.
Accordingly, a need is identified for an improved connector for the links in a modular link conveyor belt. The rod should be exceptionally strong and resistant to the effects of creep, while also being suitable for use in even the most sensitive of conveying environments (including those in which food is transported). The rod should also be easy and inexpensive to manufacture using existing techniques, and thus would not contribute significantly to the cost of the overall conveyor system (which can include hundreds or thousands of these rods) or its wear. The rod should also be usable with existing conveyors, such as in a retrofit situation, without changing the design or principles of operation.